Automatic telephone exchange



Sept. 2 1924.

J. G. ROBERTS AUTOMATIC TELEPHONE EXCHANGE Filed March 10 1906 11 Sheets-Sheet 1 Sept. 2 1924.

J. G. ROBERTS MJTOMATIC TILBPRONE IXCHAflGl Filed March 10 1906 11 Sheets-Sheet 2 Witnesses Sept. 2 1924.

J. G. ROBERTS AUTOMATIC TELEPHONE EXCHANGE Filed March 10 190 11 Sheets-Sheet 5 v WW 3:

Invenbor 5W 7 W'Ltne s ses L-M Sept. 2 1924.

J. G. ROBERTS AUTOMATIC TELEPHONE EXCHANGE Filed larch 10 1.906 11 Sheets-Sheet 4 3 Inventor m ttys r III M 0 F fin Q P O M\ Wu 9M A w .0 6 NM TN a 1 A O L a .fiw j W i Sept. 2 1924. 1,507,000

J. G. ROBERTS AUTOMATIC TELEPHONE EXCHANGE Filed March 10 1906 11 Sheets-Sheet 5 Sept. 2, 1924. 1,507,000

J. G. ROBERTS AUTOMATIC TELEPHONE sxcmmea F1100 March 10, 1906 11 Sheets-Sheet 6 Sept. 2, 1924. 1,507,000

J. G. ROBERTS AUTOMATI C TELEPHONE EXCHANGE Filed latch 10 1906 ll Sheets-Sheet 7 Sept. 2 1924.

J. G. ROBERTS AUTOMATIC TELEPHONE EXCHANGE Filed larch 1O 1.906 11 Sheets-Sheet a Sept. 2, 1924. 1,507,000

J. G. ROBERTS AUTOMA'I'I C TELEPHONE EXCHANGE 7 Filed March 10 1906 l heats-Sheet 9 III! Inn I- Sept. 2 1924. 1,507,000

J. G. ROBERTS AUTOMATIC TELEPHONE EXCHANGE Filed March 10 1906 ll Sheets-Sheet 10 Sept. 2, 1924. 1,507,000

J. G. ROBERTS AUTOMATI C TELEPHONE EXCHANGE Filed larch 10, 1906 11 sheets-Sheet l1 Patented Sept. 2, 1924 UNITED STATES PATENT OFFICE.

JOHN G. ROBERTS, OF CHICAGO, ILLINOIS, ASSIGNOB, BY MIBNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A. CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE EXCHANGE.

Application filed March 10, 1806. Serial ll'o. 305,278.

To all whom it may com-em:

Be it known that 1, JOHN G. Ronnn'rs, a citizen of the United States, residin at Chicago, in the county of Cook and tate of Illinois, have invented certain new and useful Improvements in Automatic Telephone Exchanges, of which the following is a specification.

My invention relates to a system of circuits and apparatus designed for use in a telephone exchange system wherein the operation of connecting the lines for telephonic communication is performed through the medium of mechanism operating automatically. More especially, my invention relates to a full automatic system wherein the automatic mechanism is controlled by apparatus located at the subscribers statlons. It is, however, to be understood that various features of my invention may be applied advantageously in systems of types di ering specifically from the one herein described. The principal object of my invention is to provide a system employing automatic switching apparatus or mechanism which in its 0 ration will embody the desirable features 0 the best manual switching systems and will operate in an efiicient manner.

With this main object in view I have devised circuits and apparatus, and have combined them in a complete automatic telephone exchange orgamzation capable of accommodating and roviding for the interconnection of an a most unlimited number of telephone lines, which may be either party lines,that isflineseach of which is connected with and serves a plurality of subscribers stations or independent lines, that is, lines each of which serves but a single subscribers station and wherein the several stations on a line may have their call signals or bells selectively actuated from the central oflice, and may control the mechanisms at the central oflice involved in establishing connection with other lines, and in transmitting the various signals incident to such interconnection, without requiring the provision of the customary earth connection or common return conductor, or having recourse to the use of more than two conductors between the substation, or group of substations, and the central oflice.

In the system of my invention I so or ganize the substation controlling mechanism and the central oflice selectors that a series of the selectors, such as a group selector and a line connector, operate in succession in response to current variations or impulses over a subscribers line circuit. This circuit comprises only the two conductors, such as the ordinary metallic circuit wires, which, upon the connection bein established, form the metallic circuit coiiductors for telephonic communication. The current variations controlled from the subscribers stations and transmitted over the metallic line circuit occur in successive periods and the selector or connector mechanisms at the central office operate one after another during such successive periods. At the end of each period which marks also the beginning of the next succeeding period, a current variation occurs which determines the extent of movement of one selector switch and transfers the control to the next succeeding mechanism. These operations take place under the control of a single line circult, and I am thus enabled to dispense entirely with the ground connections at the submribers stations.

The mechanism selectively operated serves upon the initiation of a call atany one the substations, to prevent any 'mtrusion upon the calling line on the part of any other line by disconnecting the circuit through which connection is completed to the calling line, and at the same time establishing a peculiar electrical condition on the terminals of the line through which connection with it is completed, thus indicating that the line is engaged. .It serves to find, in succession, trunks that are not in use extending through the roups of ten thousands, thousands, hundre s and tens to the particular line with which the calling line 18 to be connected, and, havin selected the line, it serves to test its free or usy condition. If the selected line is engaged, the mechanism responds to the peculiar electrical condition existing upon its terminals, and transmits a tone or other distinctive signal to the calling subscriber to indicate that the called line is busy; if the line is not engaged, the mechanism is actuated throu h the agenc of the controllin device at t e calling su station to select t e ringin current to which the station wanted is a apted v a constantly Q 1 am o to d, and to apply this particular current to the line. It serves, after the ringing current has been applied to the called line a certain number of times without any response from the called substation, automatically to disconnect the ringing current,

and to apply a tone or a characteristic Slg nal to the calling line to indicate that the called subscriber does not answer. If, on the other hand, the subsciber responds to the calling signal, the mechanism operates automatically to disconnect the rin 'ng current from the line, and to complete t e communication circuit between the called and the calling lines; and, finally, it serves, upon the hangin up of the telephone of the calling substation at the end of the conversation, to bring about an automatic restoration of the normal condition of the connecting and selectin circuits and apparatus.

To e ect the selective actuation of the.

central oifice mechanism throu h the medium of a single circuit extending between the substation and the central oflice, and having no earth connection at the substation, I provide a circuit controlling device at the substation which is adapted to modi the flow of current in the circuit, and p11 uce a series of impulses, each impulse aving a certain predetermined duration. The length or duration of any of the impulses may be varied by varying the relation to each other of parts of the controlling device provided for that purpose; and the duration of each pulse determines the operation of a cer tain part of the automatic mechanism at the central oifice. The organization of this mechanism is such that each impulse of current in the circuit controls the movement of one of the switches concerned in the selecting of the called line and its interconnection with the calling line, and the extent of movement of each switch is dependent upon the duration of the particular current impulse to which it is adapted to re nd. ThlS result I attain by associating with each switch and uniformly moving part, which is brought into operative relation with the movable member of the switch at the beginning of the current impulse, and which remains in operative relation with it until the impulse ends, the switch member being held in the position to which it has been advanced by suitable electrically controlled retaining mechanism.

In connection with the switches that are selectively responsive to the duration of the impulses, I provide other switches which, so to speak, distribute the impulses of the series each to its correspondin selecting switch, the distributing switch eing selectively responsive to the number of impulses, and not to their duration. I prefer to urrange these distributin or controlling,.

switches so that each w' respond to certain consecutive impulses in the series, and not to the others, the switches havin a step-bystep movement, one step for eac of the impulses to which they are responsive, and being retained in the position to which they are advanced in the last step by suitable electrically controlled mechamsm.

I am thus enabled, b providing a controlling device at the su station adapted to produce in the circuit of the line a certain number of impulses of current, each impulse hav a certain predetermined duration variabe at will to efi'ect any desired selective actuation oi the series of electrically operated-l switches at the central ofiice which are involved in the selection of the called line, its interconnection with the callicigfi line, and in the transmission to both the ing and the called lines of the appropriate signals.

In carrying my invention into efiect, I have provlded a number of new and advantageous features, among which, in addition to the method of selectively actuatingthe central ofliee mechanism through the medium of a single circuit by means of impulses of current having certain peculiar characteristics of number and duration, may be mentioned the substation interrupter or controlling device by means of which these impulses are produced and their characteristics determined; the arrangement for selectively operating the selecting switches by means of constantly moving e ectrically controlled mechanism; the organization of selecting switches and distributing, or controlling, switches in two selectively actuated and cooperating series; the arrangement whereby automatic means is operated upon a connection bein made with a multi-station line for selective y signaling the desired station thereon; the arrangement whereby the rin ing current for signalling a particular su station of a fparty line is selected through the agency 0 mechanism under the control of the calling subscriber; thearrangement whereby the selected rin in current is brought into connection wit t e called line and automatically applied for a predetermined number of times; the or anization which operates automatically to 'sconnect the ringing current from the line and to notify the calling subscriber of the nonresponse of the called subscriber at the end of the predetermined time; the organization for automatically withdrawing the ringing current and completin the circuit between the called and the calling lines upon the response of the called subscriber; and a number of other features having to do with the organization of the circuits and apparatus which will be more particularly described hereinafter.

I will describe my invention in connection with the accompanying drawings, wherein Figs. 1, 2, 3 and 4 taken together constitute a diagrammatic representation of the circuit which is involved in establishin connection between a calling and a calle subscribers line in an automatic telephone exchange equipped in accordance with my invention, and designed to accommodate up to one hundred thousand lines; Fig. 5, a front elevation, partially in section on line 55 of Fig. 7, of the substation interrupter or circuit controlling device; Fig. 6, a sectional view of the same on lines 66 of Figs. 5 and 7; Fig. 7 an end elevation of the interrupter partially broken away and in section on lines 7-7 of Figs. 5 and 6; Fig. 8, a front elevation of the outside of the interrupter with part of the enclosing shell broken away; Figs. 9, l0, and 11, detail views of parts of the interrupter; Fi 12, a front elevation of one of the se ecting switches arran ed for actuation by magnetically-controlle constantly-moving mechanism; Fig. 13 a side elevation of the same; Fig. 14, an elevation of one of the controlling or distributing switches; Fig. 15, a sectional plan view of the same; and Fig. 16, a detail view of one set of the connection terminals of the switch.

I shall first describe the mechanism concerned in the production of the current impulses in the circuit of the line and the determination of the duration or length of each impulse. This mechanism I have designed with the particular object of meeting the requirements of a system operating in accordance with my invention; but it will be understood that devices for determining the number and duration of current impulses might be produced in' a cat variety of forms, and for this reason I wish it to be understood that I do not limit my invention to its employment with the particular mechanism herein described.

The substation interrupter, or controlling device, which I find it convenient in the present instance to employ, is illustrated in Figs. 5 through 11, and is designated by the reference character G. It comprises essentially a switch g, or circuit controlling device, with mechanism for causing it to open and close its contacts a predetermined number of times, and to vary at will the length of time between interruptions. The switch and its controlling mechanism are supported on a frame consisting, in the resent instance of the base 9 from which project the pa rtitions or flanges g and g, over which an enclosing shell 9 is placed to enclose and protect the mechanism mounted within. The frame and shell may be metal, or of any suitable material. The switch 9 comprises a stationary part or anvil and a movable switch spring which normally rests upon the anvil, the sprin having a projecting portion which is a apted to be engaged by an adjusting screw gr carried on the end of a bell crank lever g pivoted to the flange g" of the frame on which the switch is mounted, the other end of the bell crank lever carrying a part 9 preferably in the form of a roller, which is adapted to be enga ed by a disk 9* having a periphery provide with alternate elevations and depressions, so that as the disk is rotated the lever g is oscillated to alternately open and close the contacts of the switch g. The disk g is carried upon the end of an elongated ratchet wheel 9 journaled at its ends in the flanges g and g of the frame. The ratchet with its associated disk, whose alternate elevations and depressions correspond with the teeth of the ratchet, is turned step by step by a series of actuating members distributed along the length of the ratchet, and each adapted to cause the advance of the ratchet through one step. These actuating parts, in the present instance, are eleven in number, and are designated g", g g, gee 924, 925 927, 928 9:50, d 931 'ig g eral construction of the actuating parts is plainly shown in Fig. 11. Each part is, in the present instance, in the form of an arin journaled at one end upon a sleeve g, which extends between the flanges of the frame approximately along the center of the device, and at the other end carries a downwardly projecting segmental horn 9 provided with a spring finger 9 adapted to enga e a tooth of the ratchet g to advance it, the flexibility of the spring finger keeping it from interfering with the advance of the ratchet by the other actuating members), and with a shoulder g which is designed to engage a sto bar 9 extending transversel across the rame, to limit the downwar movement of the actuating art and prevent it from advancing the rate et wheel more than one step. Each arm also carries a ratchet portion, preferably extending upward from the arm on the arc of a circle concentric with the shaft or sleeve upon which the arm is journaled, and having as many teeth as may be required. In the present instance, 9 9 ,12 g and g are each provided with ten teet as shown in Fig. 11, g" with four teeth, g, g and g" each with but one tooth, while g, the last member in the series, has no teeth, each arm also bears a pawl g", preferably on the side of the arm away from the ratchet, adapted to engage and 00-0 erate with the teeth of the ratchet carrie on the adjoining arm. Between certain of the actuating arms shielding members of the character illustrated in Fig. 10 are interposed. Each of these members comprises an arm fulcrumed at one end of the sleeve 9", upon which the actuating members are fulcrumed, and provided at the other end with a portion g adapted to be interposed between the pawl of one actuating member and the ratchet ortion of the next actuating member in t e series. This shielding portion g may conveniently be formed, as shown, by bending the arm laterally at right angles to its plane, the forward portion of the arm being again bent forwardly into a plane parallel with that of the rear portion of the arm and carrying a se ental enlargement 9, provided with a nurled edge adapted to roject through a corresponding slot in t e plate 9 in the front of the interrupter. Projectin laterally from the segment 9 of the shielding member is a portion 9 on an are having its center in the axis of the sleeve on which the member is journaled, and provided on its lower portion with numerals or suitable characters brought into view one at a time through a corresponding aperture in the front plate 9 to indicate the extent of dis placement of the arm about its shaft, and on the u per portion with corrugations correspon ing in number and separation with the number and separation of the characters on the lower part of the lateral projection, and designed to co-operate with a retaining finger g to hold the shielding arm in any position to which it may be moved by means ofits projecting knurled edge. Each shielding arm is also provided with a part adapted to engage the stop bar 9 to limit the downward movement of the arm. Mounted upon the shaft or sleeve g" adjacent to each of the actuating arms, and secured to the sleeve so as not to be rotatable thereon, is a collar g which serves as an abutment for a spiral sprin g the other end of which is secured to t e actuating arm, and which serves to return the arm to its normal resting position against the stop bar g after it has been displaced therefrom. No retracting springs are provided for the shielding members, which are adapted to remain in the position to which they are manually moved.

In the arran ment as described the operation of the switch 9 is effected by the return of the actuating members to their normal resting ositions, one after the other, after havin been dis laced therefrom. To provide or their isplacement, and their return to normal sition at a uniform and invariable rate 0 speed, I rovide the following mechanism: 'Ihrou the hollow shaft or sleeve 9 there exten s a shaft g", which terminates at one end in a screw-threaded portion upon which is a nut g extending over the end of the sleeve 9 to prevent the longitudinal displacement of the shaft in the sleeve, and at the other end is provided with an enlarged portion or head pinned to an extension shaft g, which is 'ournaled in the flan e g of the frame, an to the end of whic a handle 9 is secured. The hub of the first actuating arm, 9", of the series is rigidly secured to the enlarged portion of the shaft to rotate therewith, while the hubs of the other actuating and shieldin arms are, as has heretofore been stated, doosely mounted on the sleeve g so as to be capable of rotation thereon. The sleeve g is supported at one end b a screw-threaded portion of reduced diameter which passes through the flange g and is secured thereto by means of a nut, as shown, and at the other end by its engagement with the enlarged end of the shaft which is rotatable within it. To provi e for the restoration of the shaft and its associated parts after they have been turned from their normal position by means of the handle 9, I employ, in the present instance, a spiral spring 9 one end of which is suitably secured to the enlarged end of the extension shaft 9 while the other end is made fast to an abutment 9' mounted upon the frame; and in order that the restoration of the shaft from its displaced to its normal position may be at a uniform and invariable rate of speed, I employ a heavy balance wheel 9 and escapement mechanism comprising an escapement g suitably fulcrumed, and connected with the balance wheel by means of a spring 9" secured to an abutment g on the wheel, together with an escapement wheel 9 journaled upon the extension shaft g. By means of a ratchet wheel 9 rigidly secured to the escapement wheel, and adapted to be engaged by a pawl carried on an arm 9*" rigidly secured to t e extension shaft 9, I bring about the result that the movement of the shaft 9 is under the control of the escapement mechanism only in the return movement of the shaft, the pawl on arm g acting to couple the arm with the escapement wheel only in the return movement of the arm. The balance wheel is made of such relatively large mass, and the spring which connects it with the escapement is so proportioned that the movement of the escapement wheel, and the shaft which it controls, is slow and at a practically uniform rate of speed. The balance wheel, as shown, is journaled between a brid ing support g and the flange g" of the rame.

As has been stated, the hub of the actuating arm 9 the first in the series, is rigidl secured to the shaft g", and it is throu this arm that movement is imparted to t e other arms in the series in the operation of the device. When the handle 9 is turned to cause the rotation of the shaft, the arm 9 is caused to rotate, and the pawl 9" carried at the end of the arm is brought into engagement with one of theteeth of the ratchet portion of the next actuating arm in the series, the tooth en aged depending on to what extent the shiel of the intervening shielding member of arm 9 is interposed between the pawl and the ratchet with which it co-operates. As soon as the pawl of g and the ratchet of g" engage, the movement of the shaft is imparted to g" which, in turn, causes its pawl to come into engagement with the ratchet of the succeeding actuating member, and so on down the line. It will be obvious that the extent to which any one of the actuating members will be moved before movement is imparted to the next member or arm in the series will depend entirely upon the extent of interposition of the shield of the intervening shielding member between the pawl of one and the ratchet of the other; and that therefore the interval of time which will elapse between the return to its normal position of one actuating memberand the return to its normal position of the preceding actuating member of the series in the return movement of the mechanism, and hence the interval between actuations of the switch 9, may be predetermined by moving the intervening shielding member through any predetermined arc.

It will be noted that certain of the actuating members, namely, g, g, 9 and g, are provided with only one tooth with which the pawl of the preceding member of the series can engage, and "that no shielding member is interposed between either of them and the preceding actuating member. This is because the operation of the automatic mechanism which the device under description controls does not require at these points in the sequence of impulses an impulse of variable duration, and therefore it is sufficient to provide for a current impulse of any certain fixed duration by employing but one tooth, and locating it so as to insure a fixed and constant movement of the pre ceding member before movement is imparted to this member. The function of the shields at the points in the series where they are located is. so to speak, merely to provide means for efiacing or rendering inoperative all of the teeth but the first one with which engagement is permitted, and, by being made movable in their relation to the teeth of the associated ratchet, to make the position of the operative tooth variable at will.

When. in the use of the interrupter described above, a call is to be made for a particular line in the exchange, the position of each of the shieldin arms is adjusted by means f its knurlecl edge, which projects through the corresponding slot in the face plate of the device. so as to cause the num- IIPY'S or characters which appear at the apertures in the face plate, reading from left to right, to correspond with the number of the station with which connection is desired. When this is done, each shield is so interposed between its associated members as to produce certain time intervals between the starting of their respective movements when the handle is turned to set the device, and between the ending of their movements when the members are allowed to return to their normal positions. Actuating member 9 is the first to be moved from its resting position, and mem-" ber g the last; and in the return movement is the first to return to its home position and g the last, each member in succession as it returns to its home position turning the ratchet g one step, and, through the medium of the disk g and the lever causing the switch g to open and close its circuit. This succession of makes and breaks in the circuit which the switch 9 controls following each other at predetermined intervals, varying according to the operative relation of the actuating members to each other, effects the selective actuation of the central oflice mechanism in a manner hereinafter to be described. The shields, it will be observed, remain in the positions in which they are set, thus enabling the call to be repeated without the necessity of again setting up the number; while the actuating members are moved back to their normal positions each by means of its associated spring 9 put under tension in the setting movement of the handle, the return movement of the shaft merely serving through the medium of the interconnected series of members to retard their return movement and regulate the same to a constant and uniform s eed.

I will now describe the switch which I have designed to respond selectively to the duration of the current impulses determined by the substation interrupting mechanism, such as that just described. One form of switch which I find it convenient to employ, is illustrated in Figs. 12 and 13. So far as the switch mechanism proper is concerned it does not differ greatly from that employed in a well known automatic telephone exchange system, and which is illustrated and described in Patent No. 638,249, issued December 5, 1899 to Keith and Erickson. the principal feature of difference being in the organization which I have provided for effecting and controlling the movement of the movable switch members. The switch comprises, in the present instance, a frame consisting of two parallel rods in and transverse plates is" upon which are mounted the movable and stationary switch contact members and the mechanism for operatin them. The movable members k, k i and is are rigidly secured to a rod 1:, from which the are insulated by insulating sleeves is. ssociated with each of the movable member M, k, and k are a number of stationary contact members k, which may be arranged in banks of ten rows, fourteen contacts in a row, or in any other grouping which the character of the circuits which are to be controlled which has been requires. As shown, the lower movable contact member 1a is arranged to engage but a sin le contact piece It".

s is customer in a switch of this character, the movab members are adapted to be brou ht into contact with any one of the fixeg or stationary contact members by two movements, one vertical, and the other horizontal, the vertical movement being first caused to bring the movable member opposite a particular row of contacts with one of which the'connection is to be made, and the rotary movement causing the arm to sweep over the contacts in that row until it completes connection with the one desired. It has been customary to eifect this movement of the movable members of the switch by means of two electro magnets operating through the medium of stepby-step mechanism, one to raise the shaft or rod k step by step the desired distance, and the other to rotate it stop by step until the desired fixed contact is engaged. In accordance with my invention I employ, instead of this step-by-step mechanism, constantly moving parts magnetically moved into engagement with a part associated with the rod is to effect the vertical movement and the horizontal movement of the rod. The driven part, or part associated with the rod, is shown in the present instance as a cylinder k" which is adapted to be engaged. by two constantly rotating disks In" and the firstmentloned disk being adapted, when it is moved intol contact with the driven c linder k to cause the shaft or rod in with its associated switch members to move up, while the disk k when moved into contact with the driven cylinder, is adapted to impart to the rod and its associated switch arms a movement of rotation. The disks k and k are similarly arranged, both being fulcrumed in the end of levers k", respectively, and both being in engagement with constantly rotating disks in, 10", respectively, carried upon shafts k", k, respectively, which are constantly and uniformly driven by any suitable source of power. The levers k, 70', respectivel are fulcrumed u on, or concentric wit their associated s afts k" and k", and each carries, in the present instance on the end opposite the end which carries the disk, an armature which is in operative relation with electro-magnetslr: and 70, respectively, suitably mounted upon the frame of the switch. The magnet 70 also serves, in the present instance, to actuate through the medium of its armature a switch It", with which a roller is, or like part carried u on the end of the armature,

1s ada ted to brought into engagement when t e magnet is energized. In order to effect the appropriate movement of the movable switch members,

the mechanism actuated by a magnet in" is mounted so that disk k" rotates in a vertical plane 'ust out of contact with the driven cylin er in; while the mechanism actuated by magnet is is so arranged that the disk is rotates in a horizontal plane just out of contact with the driven cylinder. The drivin disks are normally held in their retrac positions by any suitable means.

With the rod or shaft 1: of the switch I associate a retracting spring k, which serves to return the switch members to their normal resting position; and, to prevent such return excepting at the proper time, I provide magnetically controlled retaining mechanism, comprlsing a vertical retaining ratchet k, a horizontal retaining ratchet 7c, and a magnet is, the armature 70 of which co-operates with two pawls k and k, the first of which is adapted to engage the teeth of the horizontal retaining ratchet k, and the latter the teeth of the vertical retainin ratchet in when the magnet is energize Upon the de-energization of the magnet the armature operates upon the pawls k and k to cause them to release their associated ratchets, whereupon the shaft in with its movable switch members is free to return to its normal osition. The vertical retaining ratchet k is made in the form of a cylinder around the circumference of which the teeth extend, so that the pawl which engages the teeth does not prevent the rotation of the shaft is after it has been raised the required distance; and likewise the horizontal retainin ratchet k is in the form of a c linder wit the teeth extending longitudin tical movement of the shaft while preventing its horizontal rotary movement.

n the operation of the switch, an impulse of current is caused to pass through magnet k, which responds by attracting its armature and brin in disk is" into contact with the driven cy 1n er in. As the disk is constantly rotated, it immediately causes an upward movement of the cylinder, and, as the speed of rotation is maintained uniform at all times, the extent of the upward movement is exactly determined by the length of time during which the impulse of current passes throu h the magnet. When the current ceases t e constantly rotating disk is" is immediately withdrawn from the cylinder, and the shaft is held in the position to which it has been moved by the engagement of retaining pawl k" with the ratchet k. The operatlon of the controlling mechanism therefipon causes an impulse of current to traverse the coils of magnet is which, responding, moves the constantly rotating disk 7: into contact with the driven cylinder and thus imparts to the shaft in and its associated switch members a movement of rotation. This movement takes place at a uniform lot! 1y thereof, to permit the ver- 7 rate, and ceases immediately upon the cessation of the current flow in the magnet k", the extent of movement thus depending upon the duration of the current impulse. The shaft is held in the position to which it has been rotated by the en agement of pawl k with ratchet is, and the switch held at the point to which it has been advanced, as long as current, which was imparted to magnet k before the operation of magnets k and It, continues to flow through retaining magnet k. When this current ceases, the

. pawls release the ratchets and the switch parts return to their normal positions. It will be observed that movable contact arm It remains in engagement with its associated contact part is during the vertical upward movement of the shaft, and is withdrawn therefrom at the outset of the movement of rotation of the arm.

In Figs. 14, 15 and 16 is illustrated another form of switch which I find it convenient to employ in the circuit of my invention. This switch does not differ greatly from types well known in the art, and does not require extended description. It comprises a frame It" arranged to be secured to any suitable support, and upon which the parts of the device are mounted. The movable contact members of the switch h, if. h and h are. mounted upon, but insulated from, a rod or shaft h. fulcrumed in the support, and provided with a spring h for returning it to its normal position when it is moved therefrom. Each movable switch member co-operates with a series of stationary or fixed contact terminals it, being adapted to com lete connection with one after the other 0 the contacts as it is swung about by the rotation of the rod. Movement is imparted to the rod and the associated switch members by means of an electromagnet h through the medium of a pawl h carried upon the armature h of the magnet, and co-operating with a ratchet 72. mounted, in the present instance. upon the upper part of the rod. The switch arms are maintained in the position to which they have been moved by means of a retaining pawl it normally held away from the ratchet h" by the engagement therewith of the armature h of another magnet h, the retaining pawl being allowed to come in contact with the ratchetwhen the magnet h is energized to attract its armature. To render the mechanism incapable of advancing the movable switch members beyond the last stationary terminal each is adapted to engage, and hence irresponsive to all but. a predetermined number of the current impulses that traverse the magnet 72-", I provide the ratchet wheel 71 with only as many teeth each for the advancing pawl and the retaining pawl as correspond with the advanced positions which the movable memhere are adapted to occupy. Any further actuation of the magnet It is thus inetl'cctive to cause a further advance of the switch arms. The magnet h is also arranged to operate a switch 12 the members of which are suitably mounted upon but insulated from the frame, the arrangement being such that the switch maintains its contacts open so long as the armature is retracted, and closes them when the magnet is energized. The switch shown associated with the magnet It, in the present instance, comprises only two'contact members: but any other number and combination of contact members may be substituted as the circuit or circuits to be controlled require. Likewise, although the present switch is illustrated as being rovided with four movable contact mem ers each adapted to co-operate with four fixed or stationary contact terminals, it will be understood that any other combination of movable and fixed members may be provided as desired.

I shall now describe the circuits by means of which the mechanism described in the foregoing, together with other apparatus which is well known and requires no detailed description, is combined in an organization through which the novel operation which is the object of my invention is attained. The circuit or anization is illustrated diagrammatically 1n Figs. 1, 2, 3 and 4 of the drawings, which illustrate two telephone lines. each provided with a plurality of substations, together with the series of circuits which would be required to link them together for conversation assuming that they were in an automatic telephone exchange adapted to serve up to one hundred thousand lines. The various controlling and interconnecting switches are diagrammatica ly indicated. and will be recognized as being similar to or of the type of the switches described in the foregoing portion of the specification. For the sake of simplicity in illustration, many parts of the mechanism which are not essential to the umh-rstamling of the circuit connections are. omilieil. including all excepting part of one lnn-izom tal row of stationary contacts in em h bank of the switches adapted for both \i-lfit'fll and horizontal movement: and for the same reason a number of batteries and earth connections are shown at difi'erent points in the figures. whereas it will be understood 1 that these batteries might be. and in most cases would be, one and the same battery adapted to supply current for the operation of the entire system, while the connections illustrated as being to earth might be to a single common return conductor.

The scheme for eflecting intcl ouueciion between any two lines in the exchange which is followed in the present instance may be briefly stated as follows: Each suhscribcrs particular thousand grou line is terminated u on the movable members of a switch which are adapted in one position to extend the line to a co-operating switch through the medium of which any particular line may be selected in case of a call outgoing from the line in question, and which are adapted in another position to connect the line with stationary contact terminals of other switches through which connection is completed with the l ne in case of a call incomin to it. The movable contact terminals 0 the co-operating switch associated with each line are adapted to complete connection with any trunk which is not busy of a'number terminating upon the stationary or fixed terminals of the switch. This trunk extends to the movable terminals of another automatic switch which may have ten rowsof fixed terminals, representing the ten groups of ten thousand lines each into which the exchange may be divided, and as many contacts in each row as there are trunk lines extending from this switch to the group of ten thousand. By causing the movable contacts of the switch to move vertically a predetermined distance, any particular group of ten thousand may be selected, and, in the horizontal movement of the switch which follows, any of the trunks extending to this group which is not busy is appropriated. The trunk thus found terminates at its other end upon the movable contacts of a switch whose ten rows represent the ten groups of one thousand lines each into which the lines of the larger group are divided, while the contacts in each row represent the number of trunks extending from this switch to the particular thousand lines represented by the row. The predetermined vertical movement of the movable members, of this switch selects the desired, and the orizontal movement fin s a trunk which is not bu and completes connection with it. The ot er end of the trunk found terminates upon the movable members of a switch whose ten rows of fixed contacts represent ten groups of a hundred each into which the group of one thousand lines is divided, and whose contacts in each row represent the trunks extending to this particular hundred. In like manner, the vertical movement of the movable members of the switch selectsthe particular hundred desired, while the horizontal movement. finds a free trunk extendin to-this hundred and makes connection 't ercwith. The other end of the trunk thus selected extends to the movable members of the switch which serves to complete connection with the particular line called, the ten rows of contacts representing the ten cups of ten into which the hundred is lvided, and the ten contacts in each row being connected with the ten individual lines which that row represents. The vertical movement of the movable member selects the proper tens grou and the horizontal movement selects an completes connection with the line desired.

I. have designated the four substations of the calling line A, A, A and A, and the four substations of the called line, A, A, A, and A. Each substation is provided with the usual telephonic apparatus, comprising in the present instance the call hell (1, a condenser a, an induction coil a, a transmitter a, telephone receiver a, and a switch hook a"; and in addition there is provided at each substation an interrupter or circuit controller G of the type hereinbefore described, or of any form which will per form the work of this interrupter. The telephone line extends from the four substations A, A, A and A in two limbs 1 and 2 to the movable terminals of a controlling switch H at the central oflice B, while the telephone line which serves substations A, A, A and A extends in two limbs 23 and 24 to the movable terminals of controllin switch H at the central ofiice designated An extension of the telephone line 1, 2 connects with the fixed or stationary contact terminals' of a number of connectin U, sub'ect, however, to the centre of switch H, whi e the limbs 23, 24 of the other telephone line extend to the fixed contact terminals of a number of connecting switches U, U", subject to the control of switch H. Each line entering the exchange has, in the present instance, a normal connection with the poles of a central battery V, one of the limbs of the line includin the ma et which serves to actuate t 0 control ing switch on the movable members of which the line terminates. To avoid confusion, this arrangement is not illustrated in the case of the line extending from substations A, A, A, and A to the central oflice; but in the case of the line extending from substations A, A, A and A, the magnet k is shown included between limb 2 of the line and the free pole of the battery V. To rovide a -return path for the current 'w 'ch flows to the line through ma et h, and at the same time to balance the ins against inductive disturbances, an inductance or retardation coil b is connected between. the limb 1 of the line and the other or grounded pole of the battery.

The switch H, as shown, is provided with four movable contact arms h, h, h, and h, mounted on but insulated from the shaft h the rotation of which is controlled by the ma et h; and, as shown, each arm is adapted normally to rest on one and to be brought into contact with three other stationary contact terminals. The first two stationary contactsof each series en aged by contact arms h and It? of the switc are connected with conductors 25 and 26 exswitches Ill] tending to the stationary contact terminals which represent the line terminating on switch H on the various connecting switches U. In their third position the arms h, k rest on dead or disconnected terminals, and in their fourth position extend the circuit of the conductors 1 and 2 of the line to conductors 3 and 4 which are connected with contact arms 2' and i of the associated finder switch I. The arm hi which is connected to earth, or the earthed pole of the battery, completes no circuit in its normal or resting position, but in its second, third and fourth positions grounds conductor 27, which is connected on switches U to the stationary terminals associated with conductors 25 and 26, and which serves as a test conductor to indicate, by its changed electrical condition when the switch H is operated, that the line 1, 2 is engaged. The arm h of the switch is connected with the free pole of the central battery V and completes no circuit either in its first, or normal, or in its second position; but in its third and fourth positions closes a conductor 28 which extends through the actuating magnet 71 of the associated finder switch I, and thence to earth or the other pole of the battery by way of the restin contact of arm 11* of that switch, and w ich also has a branch 29 extending to earth through the winding of the retaining magnet i of the switch I.

The winding of retaining magnet h is included in a conductor 33 extending between the poles of the battery, and controlled in contacts h of the actuating magnet h of the switch, the circuit being closed to energize the retaining magnet to allow the pawl h to engage the ratchet h when current flows through the windin of magnet h. It is necessary that the paw h shall be in engagement with the ratchet to retain the switch in its advanced position while the armature h of magnet h is being moved back and forth by the impulses in the line circuit to advance the switch; and in order that the pawl may not be released during the brief intervals-when the armature I1 is unattracted, and conductor 33 therefore opened at contact h, I preferably make the magnet h sluggish in its action by shunting its winding with a resistance h which serves to take the discharge of the magnet and cause current to continue to circulate in the local circuit during the momentary interruption of conductor 33. Any interruption of the circuit longer than themomentary one which occurs as the armature of magnet It moves back and forth in cansing the step-by-ste advance of the switch arms, permits the e-energization of magnet h", thus making the retainin pawl inop' erative and permitting the switch to return to its normal position. It will be understood that this result may be obtained, and

the relatively slu gish operation of retaining pawl h be e acted in a number of other we s well known in the art.

1 eferring now more particularly to the finder switch I, which is associated with controlling switch H and is individual to the line 1, 2 extending to substations A, A, A and A, this switch is structurally practically the same as the switch illustrated in Fi s. 12 and 13 of the drawings and hereinbe ore described, excepting that it has but a single row of stationary contacts for each movable switch arm, andtherefore is enabled to dispense with the mechanism for efi'ectin a vertical movement of the switch arms. his switch has four arms 6 i, i and i", the first two and the last of which, as has been previously stated, are connected to conductors 3 and 4 and to earth, res ec tively, while arm i is normally connec by way of conductor 30 to earth through the resting contacts of the switch 91 operated by the actuating magnet of the switch I, and, in the alternative position of the switch, to the portion of conductor 28 extending between the actuating magnet i and the resting contact of arm 2'. The fixed terminals. with which arms, 2, i and i are adapted to come into enga ment as they are rotated, are connects with the conductors of a number of trunk lines, the two line conductors 5, 6 of each trunk being terminated upon corresponding contacts of the series with which arms 2' and i co-operate, while the local or test conductor 31 associated with each trunk is terminated upon a corresponding contact of the series which arm i is adapted to engage. In the drawing but a single trunk 5, 6 is illustrated, with its conductors 5, 6 and 31 connected to other like finder switches I, but it will be understood that the other stationary contacts, of which there may be an desired number, of the switch I are all likewise connected to other trunks.

In the operation of the controllin switch H and the finder switch I descri the closure of the telephone switch at an one of the four substations connected with line 1, 2 closes a circuit whereby current may flow steadily out through actuating magnet h" of switch H and back through the retardation coil 6. This causes the actuating magnet to attract its armature and advance all of the arms of switch H one step, from their first or normal to their second position, which, it will be seen, does not inter rupt the circuit normally existing between line 1, 2 and conductors 25, 26 extending to the connecting switches U but merely serves to cause arm h to connect conductor 27 to earth to make line 1, 2 busy to other lines. The first of the succession of current impulses determined in the line by the operation of interrupter G at the substation above, 

